70      IMPROVEMENTS  IN  THE  MANUFACTURE  OF  POTASSIUM. 
IMPROVEMENTS  IN  THE  MANUFACTURE  OF  POTASSIUM. 
By  MM.  Mareska  and  Donny. 
The  process  ordinarily  employed  in  the  manufacture  of  Potas- 
sium, is  that  invented  by  Brunner,  which  consists  in  exposing  to 
a  very  great  heat,  an  intimate  mixture  of  charcoal  and  carbonate 
of  potash,  the  produce  of  the  calcination  of  crude  tartar.  Ex- 
perience has  shown  that  a  given  mixture  of  this  kind,  does  not 
invariably  yield  the  same  quantity  of  potassium,  notwithstanding 
the  greatest  care  which  may  be  taken. 
The  operation,  often  a  very  unproductive  one,  is  also  attended 
with  many  dangers  and  difficulties,  arising  from  obstructions  in 
the  pipes,  caused  by  deposits  of  carburetted  products ;  obstruc- 
tions which  often  occasion  disastrous  explosions.  The  attention 
of  MM.  Mareska  and  Donny  having  been  called  to  these  points, 
they  have  endeavored  to  ascertain  the  defects  of  the  present  pro- 
cess, and  to  suggest  suitable  remedies. 
Their  attention  was  first  directed  to  the  action  which  potas- 
sium suffers  from  the  carbonic  oxide,  which  is  formed  in  the 
manufacture.  It  was  well  known  that  carbonic  oxide,  which  has 
no  action  on  potassium  at  a  bright  red  heat,  has  a  very  powerful 
effect  on  it  at  lower  temperatures  ;  but  MM.  Mareska  and  Don- 
ny have  shown,  by  a  very  simple  operation,  that  when  a  mixture 
of  carbonic  oxide  and  potassium  vapor  is  collected  in  a  large  re- 
ceiver, kept  quite  cool,  the  potassium  does  not  condense  in  a  me- 
tallic state,  but  that  a  carburetted  product  is  formed,  from  whence 
the  metal  cannot  be  obtained  by  simple  distillation. 
In  Brunner's  process,  the  potassium  set  at  liberty  by  the  reac- 
tion of  carbon  on  carbonate  of  potash,  is  condensed  in  the  tube 
placed  intermediary  between  the  retort  and  the  receiver,  or  in  the 
receiver  itself,  or  else  it  is  carried  off  by  the  gases  out  of  the  ap- 
paratus. 
The  result  therefore  is,  that,  in  Brunner's  process,  the  chief  quan- 
tity of  potassium  must  be  lost,  only  a  small  portion  being  saved, 
which,  being  condensed  in  the  tube,  continues  sufficiently  fluid 
to  run  into  the  receiver,  the  portion  which  solidifies  in  the  tube 
being  there  exposed  to  the  contact  of  carbonic  oxide, 
forms  carburetted  products,  and  thus  becomes,  as  already  noticed, 
the  source  of  insurmountable  and  oftentimes  very  dangerous 
explosions. 
